A fuel injector can be used to inject high pressure fuel into a cylinder of a combustion engine. Specifically, a tip of the fuel injector has one or more small orifices disposed therein and, as the high pressure fuel is directed into the fuel injector, it passes to the cylinder by way of these orifices. To enhance operation of the combustion engine, the orifices are precisely formed to have a particular profile and opening diameters. Historically, these orifices have been straight-walled and formed through mechanical drilling or electrical discharge machining processes.
Although effective in some applications, mechanical drilling and electrical discharge machining processes can be limited. For example, it has recently been recognized that a reverse taper in an orifice of a fuel injector tip (i.e., a generally conically-shaped hole originating from a larger internal diameter and terminating at a smaller external diameter of the injector tip) can improve injection flow characteristics. Without extensive control systems, mechanical drilling and electrical discharge machining processes may be unable to produce the reverse-taper profile. And, even with the extensive control systems, these machining processes may be expensive, require significant amounts of time to create each orifice, and be size limited.
One attempt to quickly produce an inexpensive reverse-tapered orifice in a fuel injector tip is disclosed in U.S. Pat. No. 6,642,477 (the '477 patent) issued to Patel et al. on Nov. 4, 2003. In particular, the '477 patent describes a machining process whereby the orifice is drilled by a laser beam directed at an external surface of the injector tip. To create the reverse taper profile, the injector tip is tilted relative to the laser beam and moved along a rotation axis such that an ablation region, following a full 360° rotation, delimits a reverse taper within the orifice. In this manner, each orifice has a larger opening at an inaccessible side of the fuel injector tip wall than at an accessible side.
Although the laser machining process described in the '477 patent may be capable of producing an orifice having the desired taper, it still may require a complex control system. That is, because the injector tip must be rotated at a precise angle relative to the laser beam during machining, a complex workpiece mounting/rotating arrangement may be required. And, the relative rotation during machining could introduce opportunities for misalignment between the laser and injector tip that result in an undesired orifice profile. Further, because the process described in the '477 patent requires the laser machining be performed from outside of the injector tip, once a wall of the injector tip has been pierced by the laser beam, damage to an opposing internal surface of the injector tip could occur.
The present disclosure is directed to overcoming one or more of the shortcomings set forth above and/or other problems of the prior art.